1. Field of the Invention
This invention relates to a ferrule for an optical fiber connector (hereinafter referred to occasionally as "optical connector") which is used in connecting adjoining single mode optical fibers and to a method for the production thereof.
2. Description of the Prior Art
Generally, the optical fiber connector, as illustrated in FIG. 1, for example, is composed of a plug 100 to which is connected an optical fiber cord 110 having an optical fiber inserted and fixed therein along the central axis thereof and a hollow cylindrical sleeve 120 adapted to couple and align two such plugs. Unlike the electric connector, the optical fiber connector is particularly required to align exactly the opposed ends of two optical fibers to be connected.
For this purpose, ferrules 101 which are adapted for the insertion of the leading ends of two very thin optical fibers to be connected are popularly used. The connection of the two optical fibers is attained by abutting two such ferrules 101 against each other. Specifically, it is based on the procedure which comprises causing two ferrules 101 each having the leading end of an optical fiber inserted and fixed therein to be severally fixed concentrically to two plugs 100 finished in a prescribed outside diameter, inserting the two plugs 100 into one sleeve 120 through the opposite ends thereof, and abutting the ferrules 101 against each other thereby aligning the axes of the optical fibers.
As mentioned above, the ferrule for an optical fiber connector, for the sake of perfect coincidence between the axial lines of the opposed terminals of the optical fibers, requires to warrant extremely high accuracy for the inside diameter of the fine insertion hole of the ferrule which substantially retains an optical fiber and for the outside diameter of the ferrule and further requires to secure coincidence between the axial line of the fine hole and the axial line of the outside diameter.
Since the conventional ferrule has been manufactured by mechanically working a metallic material or a ceramic material, it has room for improvement in the ability of mass-production, namely the cost of fabrication. Particularly, since the ceramic material such as, for example, the partially stabilized zirconia (PSZ) is subjected to primary formation such as by the powder extrusion or injection molding and then to such steps as degreasing, sintering, and mechanical working, the process of production is lengthy, the cost of production is inevitably large, and the material which is brittle and rigid entails such problems as chipping and relying for finish of surface polishing on grain size. To fulfill the task of cost reduction, the concept of injection molding a carbon fiber-reinforced plastic composite material has been proposed. For application to the optical connector to which the ferrules are frequently attached and detached repeatedly, however, this method possibly entails such problems as deformation and deterioration on account of the properties of the material.